Fuse and anti-fuse switches typically include a thin film disposed between first and second electrodes. Such switches have been employed, for example, in memory devices, wherein a selected phase or memory state, such as xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d, is created by selectively applying current or voltage across the first and second electrodes in order to vary the conductance between the first and second electrodes. Such memory devices are typically, but not necessarily, one-time programmable or write-once memory devices. Alternatively, such memory devices can be erasable or phase-reversible to facilitate numerous read/write cycles.
One limitation of known memory devices that employ fuse or anti-fuse switches is that the electrode material is designed to serve as both part of a conduction line of the memory device, and as an electrode of the switch itself However, the optimum material for the switch electrodes is oftentimes not the optimum material for the conduction lines, thereby resulting in undesirable trade-offs. For example, a switch known as a Le Comber switch utilizes diffusive metals, such as gold (Ag), for one of the two electrodes. However, diffusive metals such as gold may not be the most desirable material for the conduction lines. One solution to this problem is to employ multi-layer metal films for conduction lines and memory cells. However, this solution requires additional processing steps that increase the cost of device fabrication.
Another limitation of known fuse or anti-fuse switches and memory devices incorporating the same is that the thin film material has anisotropic electrical properties, which requires costly photolithographic processing and limits the achievable density. For a fuse switch, the thin film material is required to exhibit low electrical resistance between the first and second electrodes, before switching (i.e., when in the xe2x80x9conxe2x80x9d state), while exhibiting high electrical resistance between neighboring switches, and is also required to exhibit high electrical resistance between the first and second electrodes, after switching (i.e., when in the xe2x80x9coffxe2x80x9d state). Anti-fuse switches require similar anisotropic electrical properties.
The present invention encompasses, among other things, a device that includes a layer of material having particles dispersed therein, a first electrode on a first surface of the layer, and a second electrode on a second surface of the layer opposite the first surface. A state of the particles is changed when a prescribed voltage is applied across the first and second electrodes.
The present invention additionally encompasses various embodiments of switches and memory cells, and devices incorporating the same.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.